We have a barrage of tests such as faecal occult blood(FOB), faecalDNA, flexible sigmoidoscopy, colonoscopy and virtual CT colonography (CTC) to address the possibility of significant colorectal neoplasia. Where do these tests fit and when should these be used individually or in combination? Before we can address this question, we need to understand the demographics of CRC. Vast majority (65-85%) of CRC occur in people who have no family history and they are referred to as average risk category patients. Some 10-30% of CRC occur in patients who have a family history of CRC and they are referred to as moderate risk category. Remaining 5-6% of CRC occur in high risk patients such as those with non-polyposis colorectal cancer syndrome (HNPCC) and rarely in adenoma- tous polyposis coli or similar rare syndromes.
Introduction: Obscure gastrointestinal bleeding (OGIB) is increasingly becoming a common problem in the aging population. These patients, typically, had at least one set of normal gastroscopy and colonoscopy without being able to detect a site of blood loss in the upper or lower gastrointestinal tract.
Eosinophilic oesophagitis (EO) has been sporadically reported since the 1970s in the children as a cause of dysphagia. In recent times, more and more cases of EO are being reported as a cause of dysphagia and food bolus obstruction in the adult. EO can cause oesophageal strictures and stiffness and is defined by more than 20 eosinophils per high power field in the proximal oesophageal biopsies. Incidence in the children has been reported to be in the range of 1.2 to 1.3 per 10,000 children. Incidence has not been worked out in the adults although some 20% cases of dysphagia or food bolus obstruction would be associated with EO. EO mainly affects the male sex in the 3rd to 4th decade in the adults . Some 7% have family history.
Virtual colonoscopy includes CT Colonography (CTC) and MR (magnetic resonance) colonography. MR colonography is very much in the developmental phase and is not available in Australia and therefore, will not be discussed here. Technique: CTC involves a) bowel cleansing, b) air or CO2 insufflation of the co- lon, c) CT scanning and d) image processing and interpretation.
While colonoscopy and polypectomy reduced incidence of bowel cancer in 76% and reduced bowel cancer related mortality in 53% in a cohort of post-polypectomy pa- tients ( National bowel cancer study), the magnitude of such prevention depends on your colonoscopist’s adenoma detection rate (ADR). Colonoscopist’s ADR is de- fined as the percentage of consecutive screening (asymptomatic) patients who had at least one adenoma removed. A colonoscopist’s ADR is inversely proportional to post-colonoscopy missed cancers and adenomas. Higher the ADR less the missed colorectal cancers (CRC) and polyps (adenomas) for these patients in the post - polypectomy years.